Cyclic sulfones of conjugated dienes



Aug. 31, 1948. F. w. ROSE, JR

cYcLIc sULFoNEs OE coNJUGATn blanks Filed D60," 29, 1942 cation of `dienes'from impurities.

Patented ug. 31, 1948 cYcLrc sULFoNEsJoF CONJUGATED BIENES Frank William Rose, Jr., Media, Pa., assignor to Houdry Process Corporation, Wilmington, Del., a corporation of Delaware Application December 29, 1942, `Serial No. 470,446

The present invention proved means for the separation of dienes from gas mixtures containing the same and to purin- There are many processes for the preparation of dienes which, result in gas mixtures containing a greater or lesser percentage of diene. -According1y,'separation and/or purification is custom- Aarily necessary; Since separation and purification are fundamentally the same, the only distinction being in the relative quantity ofimpurity, these two terms are herein used interchangeably andi without distinction throughout :the specification and claims. `With butadiene- `1,3 one of the most important production methods involves the' dehydrogenation of normal bu- -tane, normal butenes, ormixtures of the two. The C4 gas mixture so produced will generally contain between-about 10 and 50% of butadiene- 1.3. Impure butadiene-1,3 is also produced froml vinylacetylene and from ethyl alcohol. Accordingly, the purification of conjugated dienes is of substantial importance. The present invention provides means'-ior the separation and puriiication of low Vboiling conjugated dienes generally, including not only butadiene-1,3 but also conjugated pentadienes and conjugated hexadienes.

Many systemsihave been proposed for the purification of dienes. Briefly stated, lthe known 'methods are solvent extraction, gas absorption in butadiene from other C4 gases is exceedingly ex' pensive and involves yhigh reflux ratios. Neither of these methods will separate conjugated from .-non-conjugated dienes. Complexes of cuprous .salts entail mechanical diillculties. The sulfone system is disadvantageous due to limiting equilibrium conditions and to losses during liberation of th'e butadiene from the sulfone.

'I'he present invention provides new and novel methods for operating the sulfone purificationl system whereby the disadvantages encountered heretofore in this system are obviated.

It has heretofore been proposed'to .react butadiene-1.3 and sulfur dioxide for the production lofcrystalline sulfones in the presence of an inrelates to new and im- 5 Claims. (Cl. 260--329) inibitor, such as pyrogallol f prevent the formation of non-crystalline sulfone orthe like, which will which is not `desired in purification systems.

vMany suchlinhibitors are known in` the art and all such inhibitors are applicable inthe present procedure. Furthermore, it'has been proposed to react th'e conjugated diene and sulfur dioxide for the formation of crystalline sulfone eitherin gas or liquid phase or in the 'presence` of a solvent.

Regardless of the phase or the presence of a solvent the adverse equilibrium constant is not affected. It is possible to shift the equilibrium by increasing the mole ratio of sulfur dioxide to diene and in this way obtain a, higher percentage conversion of the diene to sulfone.I This procedure results in thenecessity of recoveringfa major portion of the sulfur dioxide from the gases from which only a part of the diene has been recovered. Furthermore, the use of a high mole ratio of sulfur dioxide to diene necessitates the use of a large reactor due to the volume of materials which must be handled. Other disadvantages resultfrom the fact that fory a favorable equilibrium constant it is necessary to maintain low temperatures, but at the low temperatures the rate of reaction is so low that exceptionally long times of contact would be necessary. For high rates of reaction it is necessary to go to the higher temperatures. However, atI these high temperatures the equilibrium i-s substantially less favorable than at the low temperatures. Regardless of the presence of solvents the limiting equilibria control.

4In accordance with the present;'invention an impure diene is fed continuously to a fractionating zone. Sulfur dioxide and alsojfif desired, 'a solvent for the sulfone are also introduced continuously into the reaction zone.- 4'Conditions are maintained in the fractionation zone which resuit in the formationof a sulfone of th'e diene. The sulfone is continuously withdrawn from the reaction zone and may desirably be passed to Va stripping zone wherein any residual sulfur diox- `ide or other gases are stripped therefrom. The

remaining constituents of the impure diene after removal of the diene, are continuously withdrawn from the fractionating zone and if a solvent is used may desirably be forwarded to a stripping zone in which th'e gas is stripped from residual solvent, which is returned to the fractionating zone. 4Also in accordance with the present invention the sulfone is decomposed in the presence of the solvent. After separation of the diene and the sulfur dioxide and, if desired, after a ilnal stripping for a clean-up from higher boiling inafur dioxide introduced through line 3 may be employed in any desired proportion, 4I1l.1.us. t,h e ad.- vantages of the present invention may be obtained with' a molar ratio of .sul-fur dioxide .to butadiene of less than 1. Also, the .molar ratio may be run considerably higher than 1, on the order of 5 or more. Howeyen. ratios substantially below 1 or much above 2 are not desirable a stripping zone II wherein any aromatic solvent carried by the unreacted gas is removed, and from which the solvent is returned to the reaction zone. This stripping zone I I conveniently may comprise the upper portion of the column employed for reaction zone 6. The gas leaving stripping zone Il by line I2, and which comprises vprirrcipally butadienefree "Grghydrparbons and any. excess .sulfur dioxide, may loe-..disposed in any desired manner. While this disposal does not form any portion of the present invention, a suitabledisposition is .to wash it with a solvent for sulfur dioxide, such as water, in washing zone I3, whereby the sulfurdioxide may be recycled to .the system--and whereby the C4 hydrocarbons may be vforwarded to a catalytic dehydrogenation since, when the ratio is below 1, .some `diene 'will' go through the system and not be recovered,

`while- :with' -ratios above .2, the @mountof uncomvIci ed4 .sulfur dioxide which .must be `recovered is :multiplied needlessly. Accordingly. it is .preiiferred that the .mole .ratio .of sulfur .dioxide to V.diene-be Ybetween.about :l `and about@ ":Ishismixture of C.; cut, sulfur .dioxide :and -in- :hihi-tor niis `fedcontinuously to pump ..4 which .causes zitto low through heat .exchanger -5 `for .;,introduct ion near l:the lowerend of fractionating zone 6 through line L The sulfur dioxide fand .butadiene .are :in liquid. .phase tin -.the heat-.ex- .chan-ger 5, ywhich resultsl in sulfone formation icommenoing-here. Accordingly, 'by having the heat :exchanger at ;high`ftemperature .in the .range above.. V150" .advantage may -betaken .of the high rates .of .reaction in :this range. `Intothe nupper end of f .ractionating zone 6 .there .is intro- .dnceda mixture of theremainingquanti-ty .of.in. :.hibitor and "the solvent. Introduction of ythe -fm'ixture is .efected'by :means of pump 8. :The

pointor boiling -range that-itis substantiallymon? volatile .under the conditions maintained .in .the :reaction -zone and the decomposingy zone. Suitable solvents are xylene, ethyltoluene, trimethyl- .'-benzine and. other=higher boiling aromaticuhydro- Iearbonsand petroleumfractions of properboiling .ira-nge having-a; high percentage ...of aromatics. Qthe'resclvents are water, alcohols, and ketones '1i-n which .case appropriate adjustments .of fthe temperature-.and pressure iconditions, =are .made :to-:maintain the solvent in liquid phase.

i'llhe ifractionating zone .rii Ain .whichgthe reaction `:.occmrs .may be .fofwany .suitable :construction ifor obtaining intimate contactv or a gasand-'gliquid imovingrcountercurrent. lieither a bubble -cap .column orv be .provided .with .any .suitable type of packing. Thesolvent, .to .gether. .with the .soluble- :sulfone .flowing down :through the icolumn, leaves the reaction I.izone A16 :and may be introduced into a stripping :zone .a .'lhis'stripping izone'if used should-be operatedat a lower ,temperature andrpressureythanfthe frac- .ti.onating. zone 1.6,. Gases .separated-:may convenf-ientiylbe recycledftothe intakeof pump 4f through line L0., Unreacted gas moving upwardly fin :the

.fractionating-.czonenis ;.prei:`:eraiely introducedginto For example,.it maybe plant. Incaselittleor no excess sulfur dioxide is employed, this lwashing `zone I3 may be dispensed with. if there was a slight `excess of butadiene over sulfur dioxide the {overhead from fractionation .zone may :be .recycled directly to ,dehy- .drogenation vwithoutremoval of. ,the .last itraces gf butadiene.

The fractionating Azone' 6 .is .operated ,under conditions to effect sulfone formation from the zdiene present. While .temperatures ,above `'752,11'. may .be empieyed when using .a catalyst which promotes the sulfonation ,reaction. the ,rates .of reaction `@between and ,1 50'o F. `are lowin` labsence of a catalyst .neces,sitatirigunderL these conditions alarge fraotionating zone .ingr-,dorato .obtain complete conversion. Itis therefore Ierred.particular.ly in the absence .0f @..catalylt .that -a temperature. above 159 ,be maintained inthe .'fraetienating zene- Generaliyethe temperature duri-ng reaction is ,maintained .below labout v35,0" li. iii-order:to.minimize-sidereactionamhough higher :may vbe employed :at the vexpense .of some `ef the diene. The .pressure must l.be .suehuasxte `vproducemixed :phase (liquidfvapqr) .of-fthe diene .and.suifur'diexideeinithefeelumn.

- The solution otsoluble sulfone inthe solvent, .,withdrawn .from .the stripping. y.zone.9,. .is focwarded by line Mfto fpressurereleasevalve-.1&5.and

lintroduced therefrom through line ,-I-fI. into-,decomposing zone. :I T'I. As in ,sulfonating highrates of decomposition reaction are obtainedat- ,ele- .vated temperatures. The Asolvent; .sulfone mix- ,tureds introducednear the topof thedecompos.- inggzone, .which maybea packed. or'bubblelcapped column. y.'lihiscolumn is operated preferably at faftemperature above about 200 lThe "lower 'end ofthe columnmayfbe operatedat aftemperature-fsubstantially higher than theA "temperature .inthe upper-end of ,the,co1un1n, which lattentemperatu-re. may .drop substantially below 206m-F.,

iii desired, though `no..substantial'.advantage isiobtained .thereby High temperatures \mayf.;ihe maintained in :the .lower -endy offthe column :by .the.f.use of alzheater or the like, .whereby .t1-aces .ofboth vsulfur dioxide and :butadiene are .eticoativelyn.l stripped from the solvent. .'The. material difference .in iconditions for reactionfsto, .and decomposition of the 'sulfone is .the :pressure-upon .the zone.' Thus,..while the .reaction zone :is operated at,anueleizatedy pressure the .decomposition l,zoneiisi operated at. a` substantially.lowenpressura Pressures in the-neighborhoodofatmospheric are desirable. lHigher.pressuresrnay likewise be em -ployedin ithe. decomposing zonedthoughthehpres- .sures maintained .should 'be .sull-ciently/ lowithat 'decomposition results. Slightly :elevated `vpres'- `sur-es are-.Otten :desirable iin order toamaintain la `relatively low boiling solvent finliquid phasein the. .decomposing zone. '.'Ihus, .-'if' .-.afm'aximum temperature of 300 F. is maintained in decomposition zone I1 and the solvent is ethyltoluene, a slight pressure .on the zone is maintained so that the solvent is retained in liquid phase. Solvent, together with any residue or polysulfone, is withdrawn through line I8 from the bottom of decomposing zone I1.

The mixture of butadiene and sulfur dioxide from Zone I'I may be separated in any convenient manner. Thus, the sulfur dioxide and butadiene may be separated by a selective solvent, such as water, in washing Zone I9. While water has been disclosed in the prior art as a selective solvent for the separation of butadiene from butane and .butylene the sulfur dioxide is very much more soluble in water than the butadiene and eiective separation can be made therewith. Solvent, which may be carried in slight amounts by the [butadiene-sulfur dioxide mixture is to a large extent removed in Zone I9. Any other suitable selective solvent for separating butadiene from sulfur dioxide may be employed in washing zone I9. In case the same solvent is used in zones 6 and I9 bottoms from zone I9 may be recycled directly to the reaction zone. In this event solvent withdrawn from decomposing zone I1 through line I8, after removal of residue, or other suitable purification in zone 20, is introduced into zone I9 4for use as solvent therein. Otherwise the puried solvent is recycled directly to reaction Zone 6 by line 2|.

The butadiene overhead from washing zone I 9 is relatively pure. However, a final cleanup is at times desirable, in which case it is forwarded to stripping zone- 22, in which heavy residue is separated from the butadiene. This stripping zone is not the equivalent of gas fractionation systems at present in use, which are employed to separate the butadiene from other C4 hydrocarbons. The residue' from the stripping zone 22 is present only in extremely small percentage and boils substantialy above butadiene.

The mixture of water and sulfur dioxide from washing zone I9, together with some solvent may be separated in stripping zone 23 and the sulfur dioxide returned by line 24 to the reaction zone.

I claim as my invention:

1. The process which comprises reacting a low boiling conjugated diene with sulfur dioxide to form a less volatile decomposable sulfone in a fractionating zone at temperatures such that the rate of formation of the sulione is relatively rapid and at pressures such that both sulfur dioxide and said diene are maintained in both liquid and vapor phases, simultaneously fractionally distilling the resulting mixture of decomposable sulfone and unreacted diene and sulfur dioxide in said fractionating zone to eiect a downward movement of a liquid phase comprising said decomposable sulfone and an upward movement of a gaseous phase comprising unreacted diene and sulfur dioxide within said fractionating zone, and withdrawing decomposable sulfone from said iractionating zone in an amount greater than the amount formed from said diene and sulfur dioxide at equilibrium conditions.

2. In the separation of a low boiling conjugated diene from other low boiling hydrocarbons by forming a decomposable sulfone of said diene with sul-fur dioxide; the process which comprises introducing a hydrocarbon mixture consisting of said low boiling diene and other low boiling hydrocarbons to a fractionating zone, introducing to said fractionating zone suicient sulfur dioxide to form decomposable sulfone from all of said low boiling diene introduced to said fractio-nating zone; reacting said low boiling diene with sulfur dioxide to form decomposable sulfone in said fractionating zone at a temperature such that the rate of formation of the sulfone is relatively rapid and at a pressure such that sulfur dioxide, said diene and said other low boiling hydrocarbons are maintained in both liquid and vapor phases; simultaneously fractio-nally distilling the resulting mixture of decomposable sulfone, unreacted diene and sulfur dioxide and said other low boiling hydrocarbons; removing decomposable sulfone from the bottom of said fractionating zone and removing substantially only said other low boiling hydrocarbons from the top of said fractionating zone.

3. The process of claim 1 wherein a solvent for the decomposable sulfone is continuously passed downwardly through the fractionating zone, said solvent having a volatility such that it remains substantially in the liquid phase under the conditions of temperature and pressure in the fractionating zone, whereby the decomposable sulfone is removed from said fractionating zone in solution in said solvent.

4. The process of claim 3 wherein an inhibitor to prevent the formation of noncrystalline sulfone is continuously introduced to said fractionating zone in solution in said solvent.

5. The process of claim 1 wherein the low 4boiling diene is butadiene.

FRANK WM. ROSE, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,395,050 Hooker et al. Feb. 19, 1946 1,651,666 Buc Dec. 22. 1922 

